Yes, Cyberattacks Are Perfectly Legal Under the Laws of War

By Brian Fung

March 21, 2013

What’s the fastest way to annoy someone who works in national security? Just say "cyberwarfare" on repeat and watch them combust. The term is meaningless in the worst way—it puts the imagination into paranoid overdrive and is not limited by any legal definitions. All the rules we’ve got on armed conflict today apply to ye olde bombs and bullets, not viruses and botnets.

This makes a recent study from a group of NATO experts very, very welcome. Called the Tallinn Manual, it seeks to adapt the existing laws of war to cyberspace, laying down 95 new ideas over 282 pages. Many of them are just common-sense extensions of current international principles: According to one rule, cyberwarriors must take care not to hit the same targets that are off-limits to conventional forces.

These include civilians, albeit with a crucial caveat: If you’re a civilian who’s decided to join the fight, you become a legitimate target even if you aren’t affiliated with a government or a military.

“Consider an international armed conflict in which civilian patriotic hackers independently undertake offensive cyber operations against the enemy’s forces,” the report said. In this case, your civilian status could be a liability, in that you wouldn’t enjoy the rights—like prisoner-of-war privileges—that come with being a formal combatant in the conflict. Under these cyber rules, independent hacker groups like Anonymous would almost certainly fall into this category.

The manual suggests "proportionate counter-measures" against online attacks carried out by a state are permitted. Such measures cannot involve the use of force, however, unless the original cyber-attack resulted in death or significant damage to property.

Countermeasures are typically reactive—airplanes, for example, drop flares or chaff to confuse incoming missiles. But, in cyberspace, it could mean a lot more. Since attacks can happen in seconds, there’s often little time to react, so some have taken to suggesting offensive countermeasures that would hack back, maybe even without a human’s say-so. That raises some scary possibilities—an automated exchange of cyberweapons that spirals out of control, for one. The expert manual prohibits automated retribution, but that likely won’t stop a country that’s convinced it needs the capability from getting it.

The Geneva Conventions and other laws of armed conflict may be decades old at this point, but they're still providing the basis for new legal innovations. There’s a lot more to read in the full report.